1. Field
The embodiments relate to a light emitting device, a method of fabricating the same, a light emitting device package, and a lighting system.
2. Background
Generally, a light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode can be formed by combining group III-V compound semiconductors on the periodic table. The light emitting device can represent various colors by adjusting the compositional ratio of the compound semiconductors.
When a forward voltage is applied to an LED, electrons at an n layer are combined with holes at a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be emitted. This energy is mainly emitted in the form of heat or light. The LED emits the energy in the form of light.
For instance, a nitride semiconductor has been spotlighted in the development field of optical devices and high-power electronic devices due to superior thermal stability and wide band gap energy thereof. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been commercialized and extensively used.
A lateral-type light emitting device among light emitting devices according to the related art is formed in a structure in which a nitride semiconductor layer is formed on a substrate, and two electrode layers are arranged on the nitride semiconductor layer.
Meanwhile, the lateral-type light emitting device according to the related art has a big loss caused at the active layer since mesa etching is performed with respect to a wide area. Accordingly, in order to compensate for the loss, various attempts are performed to ensure a wider active layer.
For example, according to the related art, an attempt to ensure a wider active layer is performed based on the electrical connection with the nitride semiconductor layer via a through electrode serving as a portion of an electrode layer. However, the related art has a problem in reliability since operating voltage VF is increased, and the improvement of the problem is required.
In addition, according to the related art, the light extraction efficiency may be degraded due to the light absorption of the electrode layer.